The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
As conventional condensers for use in a refrigeration cycle of automobile air-conditioners, the so-called multi-flow type heat exchangers are widely employed. One example of such a condenser is shown in International Publication No. WO 02/42706.
This heat exchanger is provided with a pair of vertical headers and a plurality of heat exchanging tubes arranged in parallel along the up-and-down direction with their opposite ends connected to the headers. The plurality of heat exchanging tubes are classified by partitions provided in the headers to thereby form a plurality of passes. A gaseous refrigerant introduced into the refrigerant inlet of one of the headers passes through each pass in turn to thereby be condensed and liquefied, and then flows out of the refrigerant outlet of one of the headers.
The size of such a heat exchanger is decided by, for example, the required heat rejection performance and the size of the installation space. A common heat exchanging tube is flat in cross-section with a width of about 20 mm.
Such a heat exchanger is usually mounted in vehicles such as automobiles or trucks. In recent years, such vehicles are strongly required to be light in weight for the purpose of improving the fuel economy and/or decreasing toxic emission gas (e.g., CO2, NOx). Accordingly, every kinds of automobile parts are required to be light in weight, and therefore the aforementioned heat exchangers are not exceptional.
Under the circumstances, in order to reduce the weight of heat exchanger, it can be contemplated to reduce the height of heat exchanging tube, reduce the thickness of external peripheral wall of the heat exchanging tube or reduce the thickness of external heat releasing fin disposed between the adjacent heat exchanging tubes.
Such methods for decreasing weight are, however, considered to be reached a limit, and a further attempt to decrease the weight based on such methods causes decreased inherent heat exchanging performance. For example, if the tube height is set to be lower, the inner perimeter of each refrigerant flow path becomes shorter, causing deteriorated heat releasing performance. If the thickness of the tube external peripheral wall is set to be thinner, the pressure resistance deteriorates. Further, if the fin thickness is set to be thinner, the temperature difference between the portion of the fin which is in contact with the tube and the central portion of the fin becomes larger, causing deteriorated heat releasing performance.
The description herein of advantages and disadvantages of various features, embodiments, methods, and apparatus disclosed in other publications is in no way intended to limit the present invention. Indeed, certain features of the invention may be capable of overcoming certain disadvantages, while still retaining some or all of the features, embodiments, methods, and apparatus disclosed therein.